Inside information on xenon adsorption in porous organic cages by NMR.

A solid porous molecular crystal formed from an organic cage, CC3, has unprecedented performance for the separation of rare gases. Here, xenon was used as an internal reporter providing extraordinarily versatile information about the gas adsorption phenomena in the cage and window cavities of the material. Xe NMR measurements combined with state-of-the-art quantum chemical calculations allowed the determination of the occupancies of the cavities, binding constants, thermodynamic parameters as well as the exchange rates of Xe between the cavities.

Ratcheting rotation or speedy spinning: EPR and dynamics of ScC@C.

Besides their technological applications, endohedral fullerenes provide ideal conditions for investigating molecular dynamics in restricted geometries. A representative of this class of systems, ScC@C displays complex intramolecular dynamics. The motion of the Sc trimer has a remarkable effect on its electron paramagnetic resonance (EPR) spectrum, which changes from a symmetric 22-peak pattern at high temperature to a single broad lineshape at low temperature.

Clathrate Structure Determination by Combining Crystal Structure Prediction with Computational and Experimental Xe NMR Spectroscopy.

An approach is presented for the structure determination of clathrates using NMR spectroscopy of enclathrated xenon to select from a set of predicted crystal structures. Crystal structure prediction methods have been used to generate an ensemble of putative structures of o- and m-fluorophenol, whose previously unknown clathrate structures have been studied by Xe NMR spectroscopy. The high sensitivity of the Xe chemical shift tensor to the chemical environment and shape of the crystalline cavity makes it ideal as a probe for porous materials.

Experimental and First-Principles NMR Analysis of Pt(II) Complexes With O,O'-Dialkyldithiophosphate Ligands.

Polycrystalline bis(dialkyldithiophosphato)Pt(II) complexes of the form [Pt{SP(OR)}] (R = ethyl, iso-propyl, iso-butyl, sec-butyl or cyclo-hexyl group) were studied using solid-state P and Pt NMR spectroscopy, to determine the influence of R to the structure of the central chromophore. The measured anisotropic chemical shift (CS) parameters for P and Pt afford more detailed chemical and structural information, as compared to isotropic CS and J couplings alone. Advanced theoretical modeling at the hybrid DFT level, including both crystal lattice and the important relativistic spin-orbit effects qualitatively reproduced the measured CS tensors, supported the experimental analysis, and provided extensive orientational information.

Encapsulation of xenon by a self-assembled Fe4L6 metallosupramolecular cage.

We report (129)Xe NMR experiments showing that a Fe4L6 metallosupramolecular cage can encapsulate xenon in water with a binding constant of 16 M(-1). The observations pave the way for exploiting metallosupramolecular cages as economical means to extract rare gases as well as (129)Xe NMR-based bio-, pH, and temperature sensors. Xe in the Fe4L6 cage has an unusual chemical shift downfield from free Xe in water.

Relativistic effects on group-12 metal nuclear shieldings.

The leading-order perturbation theory approach to relativistic effects on the nuclear magnetic shielding provides an economic method for obtaining the chemical shifts in heavy-element containing systems. The method features detailed analysis potential in terms of the different physical mechanisms affecting the shielding tensors of heavy nuclei. The perturbative nature, however, results in an increasing error with increasingly heavy elements in the system.